Dynamic vulcanization of polyurethane elastomeric material in the presence of thermoplastics

ABSTRACT

A thermoplastically processable cured rubber composition comprises a crosslinked or cured urethane polymer dispersed in a matrix made of a thermoplastic polymeric material. In one aspect, the matrix forms a continuous phase and the crosslinked urethane polymer is in the form of particles forming a non-continuous phase. The processable rubber compositions can be made by a process of dynamic vulcanization of a urethane prepolymer material in the presence of the thermoplastic matrix material. The process involves combining a urethane prepolymer, a curing agent capable of reacting with the urethane prepolymer, and a thermoplastic material to form a mixture, and heating the mixture at a temperature and for a time sufficient to effect reaction between the curing agent and the prepolymer. Mechanical energy is supplied to the mixture during the heating step so that the crosslinking or curing of the urethane prepolymer occurs while the prepolymer and thermoplastic are undergoing a mixing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/463,801 filed on Jun. 17, 2003, the disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to thermoprocessable compositionscontaining cured polyurethane elastomers. It also relates to seal andgasket type material made from the compositions and methods for theirproduction by dynamic vulcanization techniques.

BACKGROUND OF THE INVENTION

Cured elastomeric materials have a desirable set of physical propertiestypical of the elastomeric state. They show a high tendency to return totheir original sized and shape following removal of a deforming force,and they retain physical properties after repeated cycles of stretching,including strain levels up to 1000%. Based on these properties, thematerials are generally useful for making shaped articles such as sealsand gaskets.

Because they are thermoset materials, cured elastomeric materials cannot generally be processed by conventional thermoplastic techniques suchas injection molding, extrusion, or blow molding. Rather, articles mustbe fashioned from elastomeric materials by high temperature curing andcompression molding. Although these and other rubber compoundingoperations are conventional and known, they nevertheless tend to be moreexpensive and require higher capital investment than the relativelysimpler thermoplastic processing techniques. Another drawback is thatscrap generated in the manufacturing process is difficult to recycle andreuse, which further adds to the cost of manufacturing such articles.

Articles made from elastomeric materials, such as seals and gaskets, maybe subject to a wide variety of challenging environmental conditions,including exposure to high temperature, contact with corrosivechemicals, and high wear conditions during normal use. For example,bearing seals for automotive applications see high temperature in normaluse and are exposed to lubricating fluids containing basic compounds andother corrosive materials. They are also subject to wear and abrasionfrom the moving parts they act to seal. Accordingly, it is desirable tomake such articles from materials that combine elastomeric propertiesand stability or resistance to the environmental conditions.

Crosslinked polyurethane materials have excellent physical properties,such as high tensile strength and wear resistance, compared with othercross linked elastomeric materials. However, they are usually limited toa continuous service temperature of only up to about 100° C. In someapplications, the relatively low heat resistance of the polyurethanematerials is a drawback that narrows the potential use of the materials.For example, they are generally unsuitable for use in some automotiveapplications, where the in service use can be 150° C. or higher.

It would therefore be desirable to provide materials having excellentphysical properties in combination a high level of heat resistance. Inaddition, it would be desirable to provide such materials that arereadily recyclable and that can be processed by conventionalthermoplastic processing techniques.

SUMMARY OF THE INVENTION

A thermoplastically processable cured rubber composition comprises acrosslinked or cured urethane polymer dispersed in a matrix. The matrixis made of a thermoplastic polymeric material, and the composition maybe processed into an article with a tensile strength that exceeds thetensile strength of the thermoplastic polymeric material. In one aspect,the matrix forms a continuous phase and the crosslinked urethane polymeris in the form of particles forming a non-continuous phase.

The processable rubber compositions can be made by a process of dynamicvulcanization of a urethane prepolymer material in the presence of thethermoplastic matrix material. In one aspect, the method involvescombining a urethane prepolymer, a curing agent capable of reacting withthe urethane prepolymer, and a thermoplastic material to form a mixture,and heating the mixture at a temperature and for a time sufficient toeffect reaction between the curing agent and the prepolymer. Mechanicalenergy is supplied to the mixture during the heating step so that thecrosslinking or curing of the urethane prepolymer occurs while theprepolymer and thermoplastic are undergoing a mixing.

In a preferred embodiment, the method involves mixing the prepolymer andthermoplastic material for a time and at a shear rate sufficient to forma dispersion of the prepolymer in a continuous thermoplastic phase. Adispersion of prepolymer in thermoplastic is formed, wherein theprepolymer particles are preferably about 50 micrometers in diameter orless. When a proper dispersion is formed, a curing agent is added to thedispersion while continuing the mixing, and the mixture is heated whilecontinuing the mixing.

The processable compositions may be formed into cured elastomericmaterials useful for example as gaskets, seals, O-rings, and hoses.Advantageously, the compositions may be processed by standardthermoplastic techniques such as blow molding and compression molding,avoiding the use of slow thermoset and possibly high temperature rubberprocessing conditions. Scrap material generated during the manufactureof the shaped articles may be readily recycled and reused, because thematerial can be processed as a conventional thermoplastic.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

The invention provides a thermoplastically processable rubbercomposition, shaped articles made from the rubber composition, andmethods for compounding the rubber composition and forming the shapedarticle. The processable rubber composition contains a crosslinkedurethane polymer dispersed in a matrix, wherein the matrix comprises athermoplastic polymeric material. The rubber compositions of theinvention can be formed into articles that exhibit desirable elastomericproperties, yet can also be processed by standard thermoplastic methodssuch as injection molding, blow molding, and extrusion.

According to one aspect of the invention, the matrix forms a continuousphase in which the crosslinked urethane polymer is in the form ofparticles forming a non-continuous or discrete phase. In another aspect,the matrix thermoplastic polymeric material and the crosslinked urethanepolymer form co-continuous phases.

The rubber compositions of the invention are prepared by reacting aurethane prepolymer (also called a “polyurethane prepolymer”) with acuring agent while stirring or otherwise mechanically mixing theprepolymer and curing agent in the presence of a thermoplastic polymericmaterial. The thermoplastic material comprises a polymeric material thatsoftens and flows upon heating. The prepolymer reacts with the curingagent to form the crosslinked urethane polymer of the invention. Theprepolymer is generally a polymer of a polyisocyanate and a polyoland/or polyamine. It may be isocyanate-functional orhydroxyl-functional, and can have a wide variety of molecular weightsand chemical structure, according to the desired properties of therubber composition, as discussed below.

A preferred method for making rubber compositions comprises the steps ofcombining a urethane prepolymer, a curing agent capable of reacting withthe urethane prepolymer, and a thermoplastic material to form a mixture,and heating the mixture at a temperature and for a time sufficient toeffect a reaction between the curing agent and the prepolymer, whilesupplying mechanical energy to mix the mixture during the heating step.

In another aspect, the preparation of the rubber compositions is carriedout by mixing the prepolymer and the thermoplastic material in thepresence of the curing agent, and heating during the mixing to effectcure of the prepolymer in the presence of the thermoplastic material. Inyet another aspect, the method comprises mixing the prepolymer and thethermoplastic material for a time and at a shear rate sufficient to forma dispersion of the prepolymer in a continuous thermoplastic phase. Whena proper dispersion is formed, the curing agent may be added to thedispersion while continuing the mixing. The combination of theprepolymer, curing agent, and thermoplastic material is then heatedduring mixing. During the mixing and heating, the prepolymer and curingagent react to form a crosslinked urethane polymer.

Shaped elastomeric articles may be readily prepared from the rubbercompositions of the invention by conventional thermoplastic processingmethods. The shaped elastomeric materials contain a crosslinked urethanepolymer dispersed in a matrix made of a thermoplastic polymericmaterial. The shaped elastomeric articles exhibit a desirablecombination of properties such as flexibility, softness, and compressionset. In one embodiment, the shaped articles are especially suitable forsuch application as seals, gaskets, and O-rings, as well as extrudedarticles such as hoses.

The polyurethane prepolymers may be described as the reaction product ofone or more polymeric polyols, one or more polyisocyanate compounds,and, optionally, one or more chain extension agents.

Depending on the nature and molar amounts of the components used, theprepolymers may be isocyanate functional or hydroxyl functional, and cantake on a wide variety of molecular weights. In the case of thethermoplastic polyurethanes, the prepolymer may also be one withessentially equal amounts of hydroxyl and isocyanate functionality. Theprepolymers are reacted with the curing agent in the presence of thethermoplastic polymeric material to form the crosslinked urethanepolymer of the rubber compositions of the invention. In a preferredembodiment, the urethane prepolymer is a polymer of a polyisocyanate anda polyester polyol. Accordingly, the crosslinked urethane polymer formedfrom the reaction of prepolymer and curing agent may also be describedas a polymer of a polyisocyanate and a polyester polyol.

In one embodiment, an isocyanate functional prepolymer is reacted with acuring agent in the presence of the thermoplastic material. Theisocyanate prepolymer is prepared according to known methods by reactinga polymeric polyol with a polyisocyanate compound, optionally in thepresence of one or more lower molecular weight chain extension agents.The amounts of polyisocyanate and polyol components are chosen such thatthere is an excess of isocyanate. The precise amounts of polyisocyanate,polymeric polyol, and chain extender are selected according to knownprinciples in order to achieve elastomers of desired physicalproperties. It is possible to synthesize an isocyanate functionalprepolymer from individual polyisocyanate and polyol components.Alternatively, many isocyanate functional prepolymers are available ascommercial products.

The curing agent for reaction with isocyanate functional prepolymers isgenerally a hydroxyl functional component or an amine functionalcomponent. Hydroxyl functional components, or polyols, react with theisocyanates on the isocyanate functional prepolymer to form urethanelinkages in the cured urethane polymer. Amine-functional components formurea linkages upon reaction with the isocyanate groups of theprepolymer. Preferred diol curing agents include 1,4-butanediol andhydroquinone di-(beta-hydroxyethyl) ether (HQEE). In one aspect, thepolyol used as curing agent for the isocyanate functional prepolymershas a hydroxyl functionality of greater than 2. For example, a triolsuch as glycerol may be used, or a mixture of diols and triols may beused. The reaction product of a polyol of functionality greater than 2with the isocyanate functional urethane prepolymer is a crosslinkedurethane elastomer similar in structure to known cast polyurethaneelastomers.

The type of curing agent can affect the overall physical properties ofthe final product. Amine functional curing agents tend to react too fastwith the isocyanate groups of the prepolymer, so useful amines tend tobe sterically hindered (such as diethyl toluene diamine or the Diak®line of curing agents) or electronically modified for slower reaction(such as the well known methylene-bis-(ortho-chloroaniline) or MOCA).

In another aspect, the polyol used as curing agent for the isocyanatefunctional prepolymers has a functionality of about 2. In this case, thecured urethane polymer formed is similar in properties to the knownthermoplastic polyurethanes.

Rubber compositions of the invention may also be made by reacting ahydroxyl functional prepolymer with a curing agent capable of reactingwith the prepolymer. Hydroxyl functional prepolymers are made fromsimilar components as with the isocyanate functional prepolymers, exceptthat a molar access of hydroxyl component over isocyanate component isused in the synthesis. The hydroxyl functional prepolymers tend to havelower molecular weight than the isocyanate functional prepolymers. Aswas the case with the isocyanate functional prepolymers, the amount ofpolymeric polyol, chain extension agent, and polyisocyanate may bechosen according to known principles depending on the desired physicalproperties of the resulting crosslinked urethane polymer.

In one embodiment the hydroxyl functional prepolymers are crosslinked byreacting with a curing agent comprising a polyisocyanate compound. Anyof the polyisocyanate compounds discussed below, such as diisocyanates,may be used as the crosslinking agent for the hydroxyl functionalprepolymers. In a preferred embodiment, the polyisocyanate curing agentis toluene diisocyanate. In a preferred embodiment, either the hydroxylfunctional prepolymer, the polyisocyanate crosslinking agent, or bothhas a functionality greater than 2, so that upon reaction, a thermosetkind of reaction product is formed containing intra- and interchaincrosslinks. Hydroxyl functional prepolymers with a functionality ofgreater than 2 may be readily synthesized by including an amount oftriols, such as glycerol or trimethylolpropane, among the componentsused to synthesize the prepolymer. Polyisocyanate compounds with afunctionality of greater than 2 are also readily available. Examplesinclude polymeric diisocyanates such as polymeric MDI, as well astrimers of diisocyanates such as isocyanurates.

Hydroxyl functional prepolymers, which in some embodiments are alsoknown as millable gums, may also in a preferred embodiment becrosslinked by peroxides. Conventional organic peroxides may be used.Non-limiting examples include alkyl peroxides and dicumyl peroxide. Theperoxide crosslinking agent reacts with active hydrogens on the urethaneprepolymer backbone to form a crosslinked urethane polymer containinginterchain links. Active hydrogens in the hydroxyl functionalprepolymers include the alpha carbon of a diacid component used to forma polyester polyol, and a methylene hydrogen of methylene phenyldiisocyanate (MDI). For this reason, a preferred hydroxyl functionalprepolymer is based on a diisocyanate component including MDI.

Examples of high molecular weight polyol components of the prepolymersof the invention include polyester polyols, polyether polyols,polylactone polyols, polytetrahydrofuran polyols, and polycarbonatepolyols.

Polyester diols may be prepared by the condensation polymerization ofpolyacid compounds and polyol compounds. Preferably, the polyacidcompounds and polyol compounds are di-functional, i.e., diacid compoundsand diols are used to prepare substantially linear polyester diols,although minor amounts of mono-functional, tri-functional, and higherfunctionality materials (perhaps up to 5 mole percent) can be included.Suitable dicarboxylic acids include, without limitation, glutaric acid,succinic acid, malonic acid, oxalic acid, phthalic acid,hexahydrophthalic acid, adipic acid, maleic acid and mixtures of these.Suitable polyols include, without limitation, wherein the extender isselected from the group consisting of ethylene glycol, diethyleneglycol, triethylene glycol, tetraethylene glycol, propylene glycol,dipropylene glycol, tripropylene glycol, tetrapropylene glycol,cyclohexanedimethanol, 2-ethyl-1,6-hexanediol, Esterdiol 204 (sold byEastman Chemical Co.), 1,4-butanediol, 1,5-pentanediol, 1,3-propanediol,butylene glycol, neopentyl glycol, and combinations thereof. Smallamounts of triols or higher functionality polyols, such astrimethylolpropane or pentaerythritol, are sometimes included. In apreferred embodiment, the carboxylic acid includes adipic acid and thediol includes 1,4-butanediol. Typical catalysts for the esterificationpolymerization are protonic acids, Lewis acids, titanium alkoxides, anddialkyltin oxides.

Polylactone diols are polyesters formed by polymerizing a cyclic lactonemonomer. They can be prepared by reacting an initiator with a lactone oralkylene oxide chain-extension reagent. The initiator contains activehydrogens. Examples include diols such as ethylene glycol and propyleneglycol. Preferred chain-extension reagents are ε-caprolactone, ethyleneoxide, and propylene oxide. Lactones that can be ring opened by anactive hydrogen are well-known in the art. Examples of suitable lactonesinclude, without limitation, ε-caprolactone, γ-caprolactone,β-butyrolactone, β-propiolactone, γ-butyrolactone,α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone,δ-valerolactone, γ-decanolactone, δ-decanolactone, γ-nonanoic lactone,γ-octanoic lactone, and combinations of these. In one preferredembodiment, the lactone is ε-caprolactone. Lactones useful in thepractice of the invention can also be characterized by the formula:

wherein n is a positive integer of 1 to 7 and R is one or more H atoms,or substituted or unsubstituted alkyl groups of 1-7 carbon atoms. Usefulcatalysts include those mentioned above for polyester synthesis.Alternatively, the reaction can be initiated by forming a sodium salt ofthe hydroxyl group on the molecules that will react with the lactonering.

Polyether polyols contain repeating units derived from alkylene oxides.They are typically prepared by reacting an initiator containing activehydrogens with an oxirane-containing compound. Commonly used initiatorsinclude water and diols such as ethylene glycol and propylene glycol.The oxirane-containing compound is preferably an alkylene oxide orcyclic ether, especially preferably a compound selected from ethyleneoxide, propylene oxide, butylene oxide, tetrahydrofuran, andcombinations of these. Alkylene oxide polymer segments include, withoutlimitation, the polymerization products of ethylene oxide, propyleneoxide, 1,2-cyclohexene oxide, 1-butene oxide, 2-butene oxide, 1-hexeneoxide, tert-butylethylene oxide, phenyl glycidyl ether, 1-decene oxide,isobutylene oxide, cyclopentene oxide, 1-pentene oxide, and combinationsof these. The alkylene oxide polymerization is typically base-catalyzed.The polymerization may be carried out, for example, by charging thehydroxyl-functional initiator and a catalytic amount of caustic, such aspotassium hydroxide, sodium methoxide, or potassium tert-butoxide, andadding the alkylene oxide at a sufficient rate to keep the monomeravailable for reaction. Two or more different alkylene oxide monomersmay be randomly copolymerized by coincidental addition and polymerizedin blocks by sequential addition. Homopolymers or copolymers of ethyleneoxide or propylene oxide are preferred.

Polytetrahydrofuran polyols are polymers of tetrahydrofuran, usuallyformed by ring opening homopolymerization of tetrahydrofuran.Tetrahydrofuran polymerizes under known conditions to form repeatingunits of —[CH₂CH₂CH₂CH₂O]—. Tetrahydrofuran is polymerized by a cationicring-opening reaction using such counterions as SbF₆ ⁻, AsF₆ ⁻, PF₆ ⁻,SbCl₆ ⁻ ^(−, BF) ₄ ⁻, CF₃SO₃ ⁻, FSO₃ ⁻, and ClO₄ ⁻. Initiation is byformation of a tertiary oxonium ion. The polytetrahydrofuran segment canbe prepared as a “living polymer” and terminated by reaction with thehydroxyl group of a diol such as any of those mentioned above.

Aliphatic polycarbonate diols are prepared by the reaction of diols withdialkyl carbonates (such as diethyl carbonate), diphenyl carbonate, ordioxolanones (such as cyclic carbonates having five- and six-memberrings) in the presence of catalysts like alkali metal, tin catalysts, ortitanium compounds. Useful diols include, without limitation, any ofthose already mentioned. Aromatic polycarbonates are usually preparedfrom reaction of bisphenols, e.g., bisphenol A, with phosgene ordiphenyl carbonate.

In one embodiment, the polymeric diol preferably has a number averagemolecular weight (determined for example by the ASTM D-4274 method) offrom about 300 to about 4,000; more preferably from about 400 to about3,000; and still more preferably from about 500 to about 2,000.

Chain extension agents include preferably difunctional and trifunctionallow molecular weight compounds containing hydroxyl groups, amino groups,or a combination of hydroxyl and amino groups. Non-limiting examples ofdiols include ethylene glycol, propylene glycol, 1,6-hexanediol,cyclohexanedimethanol, 2-ethyl-1,6-hexanediol, 1,4-butanediol, neopentylglycol, 1,4-butanediol, and neopentyl glycol. Diamines include ethylenediamine and hexanediamine. Amino alcohols include alkanolamines such asethanolamine and propanolamine.

Useful diisocyanate compounds used to prepare the urethane prepolymersof the invention include, without limitation, isophorone diisocyanate(IPDI), methylene bis-4-cyclohexyl isocyanate (H₁₂ MDI), cyclohexanediisocyanate (CHDI), m-tetramethyl xylene diisocyanate (m-TMXDI),p-tetramethyl xylene diisocyanate (p-TMXDI), ethylene diisocyanate,1,2-diisocyanatopropane, 1,3-diisocyanatopropane, 1,6-diisocyanatohexane(hexamethylene diisocyanate or HDI), 1-4-cyclohexanebis (methyleneisocyanate) (BDI), 1,4-butylene diisocyanate, lysine diisocyanate,1,4-methylene bis(cyclohexyl isocyanate), bitolylene diisocyanate(TODI), 1-6-diisocyanato-2,2,4,4-tetramethylhexane (TMDI),1,3-bis(isocyanatomethyl)cyclohexane (H6XDI),1,6-diisocyanto-2,4,4,-trimethylhexane, the various isomers of toluenediisocyanate, meta-xylylenediisocyanate, para-xylylenediisocyanate,4-chloro-1,3-phenylene diisocyanate, naphthalene diisocyanate,1,5-tetrahydro-naphthalene diisocyanate, 4,4′-dibenzyl diisocyanate,1,2,4-benzene triisocyanate, 1,4-diisocyanato benzene, xylylenediisocyanate (XDI), and combinations thereof. Particularly useful isdiphenylmethane diisocyanate (MDI). In another preferred embodimentnaphthalene diisocyanate (NDI) is used as the diisocyanate. Polymers ofnaphthalene diisocyanate tend to have superior high temperatureproperties. Other preferred isocyanate compounds include TDI and TODI.

As noted above, an amount of trifunctional hydroxyl materials may beemployed to introduce a corresponding amount of branching in thepolyurethane elastomer. Non-limiting examples of trifunctional polyolsinclude trimethylolpropane, 1,2,6-hexanetriol and glycerol. In addition,a small amount of mono-functional compounds may be employed wheredesired to control molecular weight or to offer other advantages.Preferably the amount of trifunctional polyols or mono-functionalcompounds employed would be 5% or less based on the total weight of thereaction product.

The reaction of the polyisocyanate, polymeric diol, and chain extensionagent to form the prepolymer is typically conducted by heating thecomponents, for example by melt reaction in a twin screw extruder.Typical catalysts for this reaction include organotin catalysts such asstannous octoate. Generally, the ratio of polymeric diol,polyisocyanate, and chain extension agent can be varied within arelatively wide range depending largely on the desired prepolymerfunctionality and hardness of the final polyurethane elastomer. Forexample, the equivalent proportion of polyester polyol to chainextension agent may be within the range of 1:0 to 1:12 and, morepreferably, from 1:1 to 1:8.

The thermoplastic material making up the matrix of the invention is apolymeric material that softens and flows upon heating. In one aspect, athermoplastic material is one the melt of which can be measured, such asby ASTM D-1238 or D-2116 at a temperature above its melting point

The thermoplastic material of the invention may be selected to provideenhanced properties of the rubber/thermoplastic combination at elevatedtemperatures, preferably above 100° C. and more preferably at about 150°C. and higher. Such thermoplastics include those that maintain physicalproperties, such as at least one of tensile strength, modulus, andelongation at break to an acceptable degree at the elevated temperature.In a preferred embodiment, the thermoplastics possess physicalproperties at the elevated temperatures that are superior (i.e. highertensile strength, higher modulus, and/or higher elongation at break) tothose of the cured polyurethane rubber at a comparable temperature.

The thermoplastic polymeric material used in the invention may be athermoplastic elastomer. Thermoplastic elastomers have some physicalproperties of rubber, such as softness, flexibility and resilience, butmay be processed like thermoplastics. A transition from a melt to asolid rubber-like composition occurs fairly rapidly upon cooling. Thisis in contrast to convention elastomers which hardens slowly uponheating. Thermoplastic elastomers may be processed on conventionalplastic equipment such as injection molders and extruders. Scrap maygenerally be readily recycled.

Thermoplastic elastomers have a multi-phase structure, wherein thephases are generally intimately mixed. In many cases, the phases areheld together by graft or block copolymerization. At least one phase ismade of a material that is hard at room temperature but fluid uponheating. Another phase is a softer material that is rubber like at roomtemperature.

Some thermoplastic elastomers have an A-B-A block copolymer structure,where A represents hard segments and B is a soft segment. Because mostpolymeric materials tend to be incompatible with one another, the hardand soft segments of thermoplastic elastomers tend to associate with oneanother to form hard and soft phases. For example, the hard segmentstend to form spherical regions or domains dispersed in a continuouselastomer phase. At room temperature, the domains are hard and act asphysical crosslinks tying together elastomeric chains in a 3-D network.The domains tend to lose strength when the material is heated ordissolved in a solvent.

Other thermoplastic elastomers have a repeating structure represented by(A-B)_(n), where A represents the hard segments and B the soft segmentsas described above.

Many thermoplastic elastomers are known. They in general adapt eitherthe A-B-A triblock structure or the (A-B)_(n) repeating structure.Non-limiting examples of A-B-A type thermoplastic elastomers includepolystyrene/polysiloxane/polystyrene,polystyrene/polyethylene-co-butylene/polystyrene,polystyrene/polybutadiene/polystyrene,polystyrene/polyisoprene/polystyrene, poly-a-methylstyrene/polybutadiene/poly-α-methyl styrene, poly-α-methylstyrene/polyisoprene/poly-α-methyl styrene, andpolyethylene/polyethylene-co-butylene/polyethylene.

Non-limiting examples of thermoplastic elastomers having a (A-B)_(n)repeating structure include polyamide/polyether,polysulfone/polydimethylsiloxane, polyurethane/polyester,polyurethane/polyether, polyester/polyether,polycarbonate/polydimethylsiloxane, and polycarbonate/polyether. Amongthe most common commercially available thermoplastic elastomers arethose that contain polystyrene as the hard segment. Triblock elastomersare available with polystyrene as the hard segment and eitherpolybutadiene, polyisoprene, or polyethylene-co-butylene as the softsegment. Similarly, styrene butadiene repeating co-polymers arecommercially available, as well as polystyrene/polyisoprene repeatingpolymers.

In a preferred embodiment, a thermoplastic elastomer is used that hasalternating blocks of polyamide and polyether. Such materials arecommercially available, for example from Atofina under the Pebax® tradename. The polyamide blocks may be derived from a copolymer of a diacidcomponent and a diamine component, or may be prepared byhomopolymerization of a cyclic lactam. The polyether block is generallyderived from homo- or copolymers of cyclic ethers such as ethyleneoxide, propylene oxide, and tetrahydrofuran.

Other useful thermoplastic polymers are solid, generally high molecularweight, plastic materials. Preferably, these polymers are crystalline orsemi-crystalline polymers, and more preferably have a crystallinity ofat least 25 percent as measured by differential scanning calorimetry.Amorphous polymers with a suitably high glass transition temperature arealso acceptable as the thermoplastic polymers. The resin also preferablyhas a melt temperature or glass transition temperature in the range fromabout 80° C. to about 350° C., but the melt temperature should generallybe lower than the decomposition temperature of the thermoplasticvulcanizate.

Non-limiting examples of thermoplastic polymers include polyolefins,polyesters, nylons, polycarbonates, styrene-acrylonitrile copolymers,polyethylene terephthalate, polybutylene terephthalate, polyamides,polystyrene, polystyrene derivatives, polyphenylene oxide,polyoxymethylene, and fluorine-containing thermoplastics. Thethermoplastics may be amorphous or semi-crystalline. In a preferredembodiment, the glass transition temperature Tg of an amorphousthermoplastic is 150° C. or higher, and the melting point of asemi-crystalline or crystalline thermoplastic is about 150° C. orhigher.

Polyolefins are formed by polymerizing α-olefins such as, but notlimited to, ethylene, propylene, 1-butene, 1-hexene, 1-octene,2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene,5-methyl-1-hexene, and mixtures thereof. Copolymers of ethylene andpropylene or ethylene or propylene with another α-olefins such as1-butene, 1-hexene, 1-octene, 2-methyl-1-propene, 3-methyl-1-pentene,4-methyl-1-pentene, 5-methyl-1-hexene or mixtures thereof are alsocontemplated. These homopolymers and copolymers may be synthesized byusing any polymerization technique known in the art such as, but notlimited to, the “Phillips catalyzed reactions,” conventionalZiegler-Natta type polymerizations, and metallocene catalysis including,but not limited to, metallocene-alumoxane and metallocene-ionicactivator catalysis.

Polyester thermoplastics contain repeating ester linking units in thepolymer backbone. In one embodiment, they contain repeating unitsderived from low molecular weight diols and low molecular weightdiacids. Non-limiting examples include the commercially available gradesof polyethylene terephthalate and polybutylene terephthalate.Alternatively, the polyesters may be based on aliphatic diols andaliphatic diacids. Exemplary here the copolymers of ethylene glycol orbutanediol with adipic acid. In another embodiment, the thermoplasticpolyesters are polylactones, prepared by polymerizing a monomercontaining both hydroxyl and carboxyl functionality. Polycaprolactone isa non-limiting example of this class of thermoplastic polyester.

Polyamide thermoplastics contain repeating amide linkages in the polymerbackbone. In one embodiment, the polyamides contain repeating unitsderived from diamine and diacid monomers such as the well known nylon66, a polymer of hexamethylene diamine and adipic acid. Other nylons maybe prepared by varying the size of the diamine and diacid components.Non-limiting examples include nylon 610, nylon 612, nylon 46, and nylon6/66 copolymer. In another embodiment, the polyamides are prepared bypolymerizing a monomer with both amine and carboxyl functionality.Non-limiting examples include nylon 6 (polycaprolactam), nylon 11, andnylon 12. Other polyamides made from diamine and diacid componentsinclude the high temperature polyterephthalamide polymers containingrepeating units derived from diamines and aromatic diacids such asterephthalic acid. Commercially available examples of these include PA6T(a copolymer of hexanediamine and terephthalic acid), sold by Solvay orDuPont under the Amodel or Zytel HT tradenames, respectively and PA9T (acopolymer of nonanediamine and terephthalic acid), sold by Kuraray underthe Genestar tradename.

Other non-limiting examples of high temperature thermoplastics includepolyphenylene sulfide, liquid crystal polymers, and high temperaturepolyimides. Liquid crystal polymers are based chemically on linearpolymers containing repeating linear aromatic rings. Because of thearomatic structure, the materials form domains in the nematic melt statewith a characteristic spacing detectable by x-ray diffraction methods.Examples of materials include copolymers of hydroxybenzoic acid, orcopolymers of ethylene glycol and linear aromatic diesters such asterephthalic acid or naphthalene dicarboxylic acid.

High temperature thermoplastic polyimides include the polymeric reactionproducts of aromatic dianhydrides and aromatic diamines. They arecommercially available from a number of sources. Exemplary is thecopolymer of 1,4-benzenediamine and 1,2,4,5-benzenetetracarboxylic aciddianydride.

Thermoplastic fluorine-containing polymers may be selected from a widerange of polymers and commercial products. The polymers are meltprocessable—they soften and flow when heated, and can be readilyprocessed in thermoplastic techniques such as injection molding,extrusion, compression molding, and blow molding. The materials arereadily recyclable by melting and re-processing.

The thermoplastic polymers may be fully fluorinated or partiallyfluorinated. Fully fluorinated thermoplastic polymers include copolymersof tetrafluoroethylene and perfluoroalkyl vinyl ethers. Theperfluoroalkyl group is preferably of 1 to 6 carbon atoms. Otherexamples of copolymers are PFA (copolymer of TFE and perfluoropropylvinyl ether) and MFA (copolymer of TFE and perfluoromethyl vinyl ether).Other examples of fully fluorinated thermoplastic polymers includecopolymers of TFE with perfluoroolefins of 3 to 8 carbon atoms.Non-limiting examples include FEP (copolymer of TFE andhexafluoropropylene).

Partially fluorinated thermoplastic polymers include E-TFE (copolymer ofethylene and TFE), E-CTFE (copolymer of ethylene andchlorotrifluoroethylene), and PVDF (polyvinylidene fluoride). A numberof thermoplastic copolymers of vinylidene fluoride are also suitablethermoplastic polymers for use in the invention. These include, withoutlimitation, copolymers with perfluoroolefins such ashexafluoropropylene, and copolymers with chlorotrifluoroethylene.

Thermoplastic terpolymers may also be used. These include thermoplasticterpolymers of TFE, HFP, and vinylidene fluoride.

These and other fluorine-containing thermoplastic materials arecommercially available. Suppliers include Dyneon (3M), Daikin, AsahiGlass Fluoropolymers, Solvay/Ausimont and DuPont.

In a preferred embodiment, plasticizers, extender oils, syntheticprocessing oils, or a combination thereof may be used in thecompositions of the invention. The type of processing oil selected willtypically be consistent with that ordinarily used in conjunction withthe specific rubber or rubbers present in the composition. The extenderoils may include, but are not limited to, aromatic, naphthenic, andparaffinic extender oils. Preferred synthetic processing oils includepolylinear α-olefins.

In addition to the elastomeric material, the thermoplastic polymericmaterial, and curative, the processable rubber compositions of thisinvention may include other additives such as stabilizers processingaids, curing accelerators, fillers, pigments, adhesives, tackifiers, andwaxes. The properties of the compositions and articles of the inventionmay be modified, either before or after vulcanization, by the additionof ingredients that are conventional in the compounding of rubber,thermoplastics, and blends thereof.

A wide variety of processing aids may be used, including plasticizersand mold release agents. Non-limiting examples of processing aidsinclude Caranuba wax, phthalate ester plasticizers such asdioctylphthalate (DOP) and dibutylphthalate silicate (DBS), fatty acidsalts such as zinc stearate and sodium stearate, polyethylene wax, andkeramide. In some embodiments, high temperature processing aids arepreferred. Such include, without limitation, linear fatty alcohols suchas blends of C₁₀-C₂₈ alcohols, organosilicones, and functionalizedperfluoropolyethers. In some embodiments, the compositions contain about1 to about 15% by weight processing aids, preferably about 5 to about10% by weight.

Non-limiting examples of fillers include both organic and inorganicfillers such as, barium sulfate, zinc sulfide, carbon black, silica,titanium dioxide, clay, talc, fiber glass, fumed silica anddiscontinuous fibers such as mineral fibers, wood cellulose fibers,carbon fiber, boron fiber, and aramid fiber (Kevlar). The addition ofcarbon black, extender oil, or both, preferably prior to dynamicvulcanization, is particularly preferred. Non-limiting examples ofcarbon black fillers include SAF black, HAF black, SRP black and Austinblack. Carbon black improves the tensile strength, and an extender oilcan improve processability, the resistance to oil swell, heat stability,hysteresis, cost, and permanent set. In a preferred embodiment, fillerssuch as carbon black may make up to about 40% by weight of the totalweight of the compositions of the invention. Preferably, thecompositions comprise 1-40 weight % of filler. In other embodiments, thefiller makes up 10 to 25 weight % of the compositions.

The crosslinked or cure urethane polymer, also referred to hereingenerically as a “rubber”, is generally present as small particleswithin a continuous thermoplastic polymer matrix. A co-continuousmorphology is also possible depending on the amount of rubber relativeto thermoplastic material, the cure system, the mechanism and degree ofcure of the elastomer, and the amount and degree of mixing. Preferably,the urethane polymer is fully crosslinked/cured.

The full crosslinking can be achieved by adding an appropriate curativeor curative system to a blend of thermoplastic material and urethaneprepolymer, and curing the urethane prepolymer to the desired degreeunder conventional curing conditions. In a preferred embodiment, theprepolymer is crosslinked or cured by the process of dynamicvulcanization. The term dynamic vulcanization refers to a vulcanizationor curing process for a rubber contained in a thermoplastic composition,wherein the curable rubber (here the urethane prepolymer) is vulcanizedunder conditions of sufficiently high shear at a temperature above themelting point of the thermoplastic component. Under dynamicvulcanization conditions, the rubber is simultaneously crosslinked orcured and dispersed as particles within the thermoplastic matrix.Dynamic vulcanization is effected by mixing the elastomeric andthermoplastic components at elevated temperature in the presence of acurative in conventional mixing equipment such as roll mills, Moriyamamixers, Banbury mixers, Brabender mixers, continuous mixers, mixingextruders such as single and twin-screw extruders, and the like. Anadvantageous characteristic of dynamically cured compositions is that,notwithstanding the fact that the elastomeric component is fully cured,the compositions can be processed and reprocessed by conventionalplastic processing techniques such as extrusion, injection molding andcompression molding. Scrap or flashing can be salvaged and reprocessed.

Heating and mixing or mastication at vulcanization temperatures aregenerally adequate to complete the vulcanization reaction in a fewminutes or less, but if shorter vulcanization times are desired, highertemperatures and/or higher shear may be used. A suitable range ofvulcanization temperature is from about the melting temperature of thethermoplastic material (typically 120° C.) to about 300° C. or more.Typically, the range is from about 150° C. to about 250° C. A preferredrange of vulcanization temperatures is from about 180° C. to about 220°C. It is preferred that mixing continue without interruption untilvulcanization of the urethane prepolymer occurs or is complete.

After dynamic vulcanization, a homogeneous mixture is obtained, whereinthe rubber (comprising the crosslinked or cured urethane polymer) is inthe form of small dispersed particles essentially of an average particlesize smaller than about 50 μm, preferably of an average particle sizesmaller than about 25 μm, more preferably of an average size smallerthan about 10 μm or less, and still more preferably of an averageparticle size of 5 μm or less.

The progress of the cure during the dynamic vulcanization may befollowed by monitoring mixing torque or mixing energy requirementsduring mixing. The mixing torque or mixing energy curve generally goesthrough a maximum after which mixing can be continued somewhat longer toimprove the fabricability of the blend. If desired, one can addadditional ingredients, such as the stabilizer package, after thedynamic vulcanization is complete. The stabilizer package is preferablyadded to the thermoplastic vulcanizate after vulcanization has beenessentially completed, i.e., the curative has been essentially consumed.

The processable rubber compositions of the invention may be manufacturedin a batch process or a continuous process.

In a batch process, predetermined charges of urethane prepolymer,thermoplastic material and curative agents are added to a mixingapparatus. In a typical batch procedure, the prepolymer andthermoplastic material are first mixed, blended, masticated or otherwisephysically combined until a desired particle size of prepolymer isprovided in a continuous phase of thermoplastic material. When thestructure of the elastomeric material is as desired, a curative agentmay be added while continuing to apply mechanical energy to mix theelastomeric material and thermoplastic material. Curing is effected byheating or continuing to heat the mixing combination of thermoplasticand prepolymer in the presence of the curative agent. When cure iscomplete, the processable rubber composition may be removed from thereaction vessel (mixing chamber) for further processing.

It is preferred to mix the prepolymer and thermoplastic material at atemperature where the thermoplastic material softens and flows. If sucha temperature is below that at which the curative agent is activated,the curative agent may be a part of the mixture during the initialparticle dispersion step of the batch process. In some embodiments, acurative is combined with the prepolymer and polymeric material at atemperature below the curing temperature. When the desired dispersion isachieved, the temperature may be increased to effect cure. However, ifthe curative agent is activated at the temperature of initial mixing, itis preferred to leave out the curative until the desired particle sizedistribution of the prepolymer in the thermoplastic matrix is achieved.In another embodiment, curative is added after the prepolymer andthermoplastic material are mixed. Thereafter, in a preferred embodiment,the curative agent is added to a mixture of prepolymer particles inthermoplastic material while the entire mixture continues to bemechanically stirred, agitated or otherwise mixed.

Continuous processes may also be used to prepare the processable rubbercompositions of the invention. In a preferred embodiment, a twin screwextruder apparatus, either co-rotation or counter-rotation screw type,is provided with ports for material addition and reaction chambers madeup of modular components of the twin screw apparatus. In a typicalcontinuous procedure, thermoplastic material and a solid prepolymer arecombined by inserting them into the screw extruder together in a firsthopper using a feeder (loss-in-weight or volumetric feeder). Temperatureand screw parameters may be adjusted to provide a proper temperature andshear to effect the desired mixing and particle size distribution of theuncured prepolymer in a thermoplastic material matrix. The duration ofmixing may be controlled by providing a longer or shorter length ofextrusion apparatus or by controlling the speed of screw rotation forthe mixture of prepolymer and thermoplastic material to go throughduring the mixing phase. The degree of mixing may also be controlled bythe mixing screw element configuration in the screw shaft, such asintensive, medium or mild screw conditions. Then, at a downstream port,by using a side feeder (loss-in-weight or volumetric feeder), thecurative agent may be added continuously to the mixture of thermoplasticmaterial and prepolymer as it continues to travel down the twin screwextrusion pathway. Downstream of the curative additive port, the mixingparameters and transit time may be varied as described above. Byadjusting the shear rate, temperature, duration of mixing, mixing screwelement configuration, as well as the time of adding the curative agent,processable rubber compositions of the invention may be made in acontinuous process.

When the prepolymer is a liquid (which is usually the case with thetypical cast elastomer components), the thermoplastic material may bemelted in the screw extruder, and the liquid prepolymer injected with aliquid injector into the molten thermoplastic. The curative agent maythen be added downstream of the prepolymer liquid injector.Alternatively, the liquid prepolymer and curative agent may be combinedfor a brief period before injecting the combination of prepolymer andcurative into the molten thermoplastic. The temperature and duration ofthis combining prior to injection into the molten thermoplastic arechosen such that the polyurethane rubber is not subject to a completecure before combining with the thermoplastic. Curing of the polyurethanerubber is completed in the twin screw extruder after injection of thecurative and prepolymer into the molten thermoplastic stream.

The compositions and articles of the invention will contain a sufficientamount of vulcanized elastomeric material (“rubber”) to form a rubberycomposition of matter, that is, they will exhibit a desirablecombination of flexibility, softness, and compression set. Preferably,the compositions should comprise at least about 25 parts by weightrubber, preferably at least about 35 parts by weight rubber, even morepreferably at least about 45 parts by weight rubber, and still morepreferably at least about 50 parts by weight rubber per 100 parts byweight of the rubber and thermoplastic polymer combined. The amount ofcured rubber within the thermoplastic vulcanizate is generally fromabout 5 to about 95 percent by weight, preferably from about 35 to about90 percent by weight, and more preferably from about 50 to about 90percent by weight, and more preferably from about 50 to about 80 percentby weight, based on the total weight of the rubber and the thermoplasticpolymer combined.

The amount of thermoplastic polymer within the processable rubbercompositions of the invention is generally from about 5 to about 95percent by weight, preferably from about 15 to about 65 percent byweight and more preferably from about 20 to about 50 percent by weightof the total weight of the rubber and the thermoplastic combined.

As noted above, the processable rubber compositions and shaped articlesof the invention include a cured rubber and a thermoplastic polymer.Preferably, the thermoplastic vulcanizate that makes up the compositionand the shaped articles is a homogeneous mixture wherein the rubber isin the form of finely-divided and well-dispersed rubber particles withina non-vulcanized matrix. It should be understood, however, that thethermoplastic vulcanizates of the this invention are not limited tothose containing discrete phases inasmuch as the compositions of thisinvention may also include other morphologies such as co-continuousmorphologies. In especially preferred embodiments, the rubber particleshave an average particle size smaller than about 50 μm, more preferablysmaller than about 25 μm, even more preferably smaller than about 10 μmor less, and still more preferably smaller than about 5 μm.

Advantageously, in a preferred embodiment, the shaped articles of theinvention, are rubber-like materials that, unlike conventional rubbers,can be processed and recycled like thermoplastic materials. Thesematerials are rubber like to the extent that they will retract to lessthan 1.5 times their original length within one minute after beingstretched at room temperature to twice its original length and held forone minute before release, as defined in ASTM D1566. Also, thesematerials satisfy the tensile set requirements set forth in ASTM D412,and they also satisfy the elastic requirements for compression set perASTM D395.

The reprocessability of the rubber compositions of the invention may beexploited to provide a method for reducing the costs of a manufacturingprocess for making shaped rubber articles. The method involves recyclingscrap generated during the manufacturing process to make other newshaped articles. Because the compositions of the invention and theshaped articles made from the compositions are thermally processable,scrap may readily be recycled for re-use by collecting the scrap,optionally cutting, shredding, grinding, milling, otherwise comminutingthe scrap material, and re-processing the material by conventionalthermoplastic techniques. Techniques for forming shaped articles fromthe recovered scrap material are in general the same as those used toform the shaped articles—the conventional thermoplastic techniquesinclude, without limitation, blow molding, injection molding,compression molding, and extrusion.

The re-use of the scrap material reduces the costs of the manufacturingprocess by reducing the material cost of the method. Scrap may begenerated in a variety of ways during a manufacturing process for makingshaped rubber articles. For example, off-spec materials may be produced.Even when on-spec materials are produced, manufacturing processes forshaped rubber articles tend to produce waste, either throughinadvertence or through process design, such as the material in spruesof injection molded parts. The re-use of such materials throughrecycling reduces the material and thus the overall costs of themanufacturing process.

For thermoset rubbers, such off spec materials usually can not berecycled into making more shaped articles, because the material can notbe readily re-processed by the same techniques as were used to form theshaped articles in the first place. Recycling efforts in the case ofthermoset rubbers are usually limited to grinding up the scrap and theusing the grinds as raw material in a number products other than thoseproduced by thermoplastic processing techniques.

The invention has been described above with respect to preferredembodiments. Further non-limiting description of the invention is givenin the Examples that follow. The description of the invention is merelyexemplary in nature and, thus, variations that do not depart from thegist of the invention are intended to be within the scope of theinvention. Such variations are not to be regarded as a departure fromthe spirit and scope of the invention, the extent of which is set forthin the appended claims.

EXAMPLES

Examples 1-5 illustrate the curing of a hydroxyl functional urethaneprepolymer in the presence of a thermoplastic elastomer containingblocks of polyamide and polyether. In examples 1-5, Noxtite MS-640S is amillable gum based on a prepolymer made from MDI and poly(butanedioladipate), commercially available from Unimatec Co. Ltd. of Japan. PebaxMX1205 is a thermoplastic elastomer containing blocks of polyamide andpolyether, commercially available from Atofina. Dicumyl peroxide isadded to Examples 1-5 as the curing agent.

In Examples 1-5, the Pebax MX1205, carbon black, and stearic acid arepreheated in a Brabender mixer to a temperature of 180° C. to melt thethermoplastic. The Noxtite MS 640S millable gum is then added to theBrabender mixer, and premixed together with the Pebax material for afurther 20 minutes at 30 rpm. Thereafter, the dicumyl peroxide curingagent is added to the stirred molten mixture, and heating and stirringcontinued for an additional 30 minutes. Cure is complete when the torquereading on the Brabender mixer reaches the steady state. The mixedrubber composition is then removed from the mixer and pressed on ahydraulic press to make plaques for physical property measurements.

Examples 1-5 show a series of reactions with increasing levels of PebaxMX1205 thermoplastic elastomer from 25 pphr (parts per hundred resin) to125 pphr. Tensile strength measurements at 100° C. are also reported inExamples 1-5. Examples 1-5 demonstrate an improvement in the tensilestrength at 100° C. as compared to the tensile strength of 100% curedpolyurethane.

In Examples 6-10, Unimatec U801-P is an isocyanate-functional prepolymerbased on a reaction product of TODI and polycaprolactone, available fromUnimatec. Pebax MX1205 is the thermoplastic elastomer from Atofinadescribed above, and Unimatec U801-C is a hardener available fromUnimatec that consists of diol and triol components.

Examples 6-10 illustrate the curing of a castable polyurethane elastomerin the presence of a Pebax type thermoplastic elastomer. In Examples6-10, the Unimatec U801-P prepolymer is premixed with the hardenerUnimatec U801-C for one minute at 100° C. in a separate container toobtain a partially cured crosslinked polyurethane. The thermoplasticPebax Mx 1205 is melted in a Brabender mixture at 180° C. The partiallycured polyurethane is poured into the molten thermoplastic elastomer inthe Brabender batch mixture. The molten thermoplastic and partiallycured polyurethane are mixed for about 15 to 20 minutes at about 30 rpmuntil a homogenous mixture is achieved and the polyurethane iscompletely cured, as indicated by a constant torque reading on theBrabender mixer. Example 1 Example 2 Example 3 Example 4 Example 5Ingredient pphr g pphr g pphr g pphr g pphr g Noxtite MS-640S 100.0133.0 100.0 116.3 100.0 103.3 100.0 92.9 100.0 84.4 Pebax MX1205 25.033.3 50.0 58.1 75.0 77.5 100.0 92.9 125.0 105.5 HAF Carbon Black 40.059.9 45.0 52.3 45.0 46.5 45.0 41.8 45.0 38.0 Stearic Acid 0.2 0.3 0.20.2 0.2 0.2 0.2 0.2 0.2 0.2 Dicumyl Peroxide 3.5 4.7 3.5 4.1 3.5 3.6 3.53.3 3.5 3.0 Tensile Strength at 8.33 8.81 7.89 8.72 9.3 100° C. (MPa)Example 6 Example 7 Example 8 Example 9 Example 10 Ingredient pphr Gpphr G pphr g pphr g pphr g Unimatec U801-P 100.0 174.3 100.0 146.6100.0 126.5 100.0 111.3 100.0 99.3 Pebax MX1205 25.0 43.6 50.0 73.3 75.094.9 100.0 111.3 125.0 124.2 Unimatec U801-C 7.6 13.2 7.6 11.1 7.6 9.67.6 8.5 7.6 7.5 Tensile Strength 0.2 16.98 15.64 14.42 14.98 11.75 100°C. (MPa)

1. A thermoplastically processable cured rubber composition prepared bydynamic vulcanization of a liquid urethane prepolymer material in thepresence of a thermoplastic polymeric material and at least one curingagent, the composition comprising a crosslinked urethane polymerdispersed in a matrix, the matrix comprising the thermoplastic polymericmaterial.
 2. A processable rubber composition according to claim 1,wherein the composition may be processed into an article with a tensilestrength that exceeds the tensile strength of the thermoplasticpolymeric material.
 3. A composition according to claim 1, wherein thematrix forms a continuous phase.
 4. A composition according to claim 1,wherein the crosslinked urethane polymer is in the form of particlesforming a non-continuous phase.
 5. A composition according to claim 1,wherein the crosslinked urethane polymer and the matrix formco-continuous phases.
 6. A composition according to claim 1, wherein theurethane polymer comprises a polymer of a polyisocyanate and a polyesterpolyol.
 7. A composition according to claim 6, wherein the polyesterpolyol is a lactone polymer.
 8. A composition according to claim 6,wherein the polyester polyol is a polymer of a diacid component and adiol component.
 9. A composition according to claim 6, wherein thepolyisocyanate is selected from the group consisting of naphthalenediisocyanate, methylene phenyl diisocyanate, toluene diisocyanate, andbitolylene diisocyanate.
 10. A composition according to claim 1, whereinthe urethane polymer comprises a polymer of a polyisocyanate and apolycarbonate polyol.
 11. A composition according to claim 1, whereinthe crosslinked urethane polymer is the reaction product of a isocyanatefunctional urethane prepolymer and a polyol of functionality greaterthan
 2. 12. A composition according to claim 1, wherein the crosslinkedurethane polymer is the reaction product of an isocyanate functionalurethane prepolymer and a polyol of functionality of about
 2. 13. Acomposition according to claim 1, wherein the crosslinked urethanepolymer is the reaction product of a hydroxyl functional urethaneprepolymer and a polyisocyanate.
 14. A composition according to claim 1,wherein the crosslinked urethane polymer is the reaction product of ahydroxyl functional urethane prepolymer and a peroxide curing agent. 15.A composition according to claim 1, wherein the crosslinked urethanepolymer is a cast urethane elastomer.
 16. A composition according toclaim 1, wherein the crosslinked urethane polymer is a thermoplasticpolyurethane.
 17. A composition according to claim 1, wherein thecrosslinked urethane polymer is a cured millable gum. 18-27. (canceled)28. A method according to claim 27, wherein the prepolymer is a solid,the method comprising inserting the thermoplastic material andprepolymer into the screw extruder together using a first feeder, andadding the curative agent with a side feeder at a second feederdownstream of the first feeder.
 29. (canceled)
 30. A shaped elastomericarticle comprising a thermoplastically processable cured rubbercomposition prepared by dynamic vulcanization of a liquid urethaneprepolymer material in the presence of a thermoplastic polymericmaterial and at least one curing agent, the composition comprising acrosslinked urethane polymer dispersed in a matrix, wherein the matrixcomprises the thermoplastic polymeric material.
 31. An article accordingto claim 30, wherein the thermoplastic polymeric material comprises athermoplastic elastomer.
 32. An article according to claim 31, whereinthe thermoplastic elastomer comprises a (A-B)_(n)-type polymer withblocks of polyamide and blocks of polyether.
 33. An article according toclaim 31, wherein the thermoplastic elastomer comprises a (A-B)_(n)-typepolymer with blocks of polyester and polyether.
 34. An article accordingto claim 30, wherein the thermoplastic material comprises an amorphouspolymeric material.
 35. An article according to claim 30, wherein the Tgof the amorphous polymeric material is 150° C. or greater.
 36. Anarticle according to claim 30, wherein the thermoplastic materialcomprises a semi-crystalline polymeric material.
 37. An articleaccording to claim 36, wherein the melting point of the semi-crystallinepolymeric material is 150° C. or greater.
 38. An article according toclaim 30, wherein the thermoplastic material comprises a polyamide. 39.An article according to claim 30, wherein the thermoplastic materialcomprises a polyester.
 40. An article according to claim 30, wherein thecrosslinked urethane polymer is a polymer of bitolyene diisocyanate anda polylactone diol.
 41. An article according to claim 30, wherein thecrosslinked urethane polymer is a peroxide cured polymer of methylenephenyl diisocyanate and a polyester diol.
 42. An article according toclaim 30, wherein the crosslinked urethane polymer is a polymer ofbitolyene diisocyanate and a polycarbonate diol.
 43. A seal according toclaim
 30. 44. An O-ring according to claim 30
 45. A gasket according toclaim
 30. 46. A method for reducing costs of a manufacturing process formaking shaped rubber articles from a processable rubber composition,comprising recycling scrap material generated during the manufacturingprocess to make new shaped articles comprising the processable rubbercomposition, wherein the processable rubber composition is the productof dynamic vulcanization of a urethane prepolymer in the presence of athermoplastic material.
 47. A method according to claim 46, wherein themanufacturing process comprises forming the shaped articles by athermoplastic processing technique.
 48. A method according to claim 47,wherein the thermoplastic processing technique is selected from thegroup consisting of blow molding, injection molding, compressionmolding, and extrusion.